Opening and second day I used a .410. 2 1/2” 1/2 ounce #8 then 7’s. Winchester Model 42 full choke. Early birds are fairly easy but after two days of pounding they can get much wiser. I do limit my range to not wound birds unnecessarily but will use that #7 load if needed to anchor a cripple. Opening day was 15/21, day two was 15/27. I was on the end station where birds were climbing to go over the tree tops so closest bird was about 18 yards with most 22-25 yards. Best thing this year was breaking in a new lab. She was a joy to watch and recovered 100% of my birds.

I have tried 3” shells but found few which patterned well with enough velocity to be a longer range .410 option. Stan has the right plan with plated shot I think. I use the standard 1/2 ounce mag 8&7’s at 1300 FPS or a bit more. Too much faster and I get blown patterns. Perhaps with slightly different chokes you might find a sweet spot.